An internal combustion engine comprises a cylinder head and a cylinder block which form one or more combustion chamber. In a multi-cylinder combustion engine it is desirable for the combustion events in all of the cylinders to be homogenous. An important factor for achieving uniform combustion events is to maintain the same wall temperature for all of the combustion chambers. This requires consistent cooling of each cylinder within the internal combustion engine. A coolant circuit comprising a plurality of coolant passages is normally provided in the cylinder head. The coolant circuit is configured to supply a continuous, controlled flow of a liquid coolant, typically a water-based coolant, through the coolant passages. The coolant passages are arranged proximal to the combustion chambers to extract the thermal energy conducted through the chamber walls. A single coolant pump is typically provided to circulate the coolant through the coolant passages. The flow from the coolant pump is divided into several flow streams and supplied to each cylinder coolant jacket. Dividing a single flow stream into multiple flow streams having the same mass flow rate can be problematic. In general terms, when a single inlet passage is split into multiple passages, the direction of the bulk fluid flow from the inlet passage causes a flow bias in those passages more closely aligned with the inlet flow. To reduce or minimise this flow bias may require considerable design work to achieve an acceptable solution across the complete operating range of the engine. This may result in restricted flow causing pressure flow losses that result in excessive pump power expenditure and excessive fuel usage.
It is against this backdrop that the present invention has been conceived. At least in certain embodiments, the present invention seeks to overcome or ameliorate at least some of the problems associated with prior art coolant circuits.